Cost of revenues related to sales of services increased by 30.1% to $10.1 million in the six months ended June 30, 2021, from $7.8 million in the same period in 2020. This increase is primarily attributable to higher support personnel expenses associated with providing services and implementation of our products with service providers as well as enterprise customers. Gross margin percentage from services was 77.3% in the six-month period ended June 30, 2021 and 77.7% in the same period in 2020.
Research and Development Expenses, net. Research and development expenses, net, consist primarily of salaries and related costs of employees engaged in ongoing research and development activities, development-related raw materials and the cost of subcontractors. Research and development expenses, net increased by 8.6% to $24.8 million in the six months ended June 30, 2021, from $22.8 million in the same period in 2020. As a percentage of total revenues, Research and development expenses, net decreased to 20.7% in the six months ended June 30, 2021, from 21.6% in the same period in 2020. The increase on an absolute basis is due to an increase in the expenses related to share-based compensation and an increase in the number of employees and related expenses associated with the additional employees. Expenses included in research and development expenses related to share-based compensation were $1.2 million, compared to $0.5 million in the same period in 2020.
Selling and Marketing Expenses. Selling and marketing expenses consist primarily of salaries and related costs (including sales commissions) of sales and marketing personnel, as well as exhibition, travel and related expenses. Selling and marketing expenses increased by 16% in the six months ended June 30, 2021 to $29.7 million, from $25.6 million in the same period in 2020 and increased as a percentage of revenues to 24.9% in the six months ended June 30, 2021, from 24.2% in the same period in 2020. The increase on an absolute basis is due to an increase in the expenses related to share-based compensation and an increase in the number of employees and related expenses associated with the additional employees. We added employees in an effort to increase our market share in the areas in which we sell our products and services, mainly due to our continued progress in pivoting to recurring revenues. This increase was partially offset by a decrease in travel, conferences and exhibitions expenses due to COVID-19. Expenses included in research and development expenses related to share-based compensation were $2.8 million, compared to $1.6 million in the same period in 2020.
General and Administrative Expenses. General and administrative expenses consist primarily of salaries and related costs of finance, human resources and general management personnel, rent, network and allowance for doubtful accounts, as well as insurance and consultant services expenses. General and administrative expenses increased by 15.9% to $7.6 million in the six months ended June 30, 2021, from $6.6 million in the same period in 2020. As a percentage of revenues, general and administrative expenses increased to 6.4% in the six months ended June 30, 2021, from 6.3% in the same period in 2020. The increase on an absolute basis is primarily due to an increase in the expenses related to share-based compensation. Expenses included in general and administrative expenses related to share-based compensation were $2.1 million, compared to $1.3 million in the same period in 2020.
Financial Income (expenses), Net. Financial Income, net consists primarily of interest earned on cash and cash equivalents, marketable securities and bank deposits, net of interest on our bank loans and bank charges. Financial income, net, in the six months ended June 30, 2021 was $1 million, compared to $0.5 million in the same period in 2020. The increase in financial income, net in the six months ended June 30, 2021 was primarily due to interest income recorded with respect to marketable securities.
Taxes on Income. We had net income tax expenses of $3.0 million in the six months ended June 30, 2021 compared to $3.6 million in the same period in 2020. The decrease in net income tax expenses in the six months ended June 30, 2021 is mainly resulted from the decrease in deferred tax asset due to utilization against income before taxes on income.
Liquidity and Capital Resources
We finance our operations primarily from our cash and cash equivalents, bank deposits, bank borrowings and cash from operations. In addition, in June 2020 we realized net proceeds of approximately $85.4 million as a result of a public offering.
As of June 30, 2021, we had $191.9 million in cash and Cash and cash equivalents, long and short-term bank deposits and long and short-term marketable securities, compared to $186.3 million as of December 31, 2020. This increase is the result of cash provided by operating activities offset, in part, by the use of cash to repurchase our ordinary shares pursuant to our share repurchase program and the payment of a cash dividend in the first quarter of 2021. We were restricted with respect to using approximately $5.7 million of our cash as a result of provisions in our loan agreements and lease agreement.
Share Repurchase Program and Cash Dividends
On February 4, 2021, we declared a cash dividend of $0.16 per share. The dividend, in the aggregate amount of approximately $5.3 million, was paid on March 4, 2021 to all of the Company’s shareholders of record on February 18, 2021.
During the six months ended June 30, 2021, we acquired 586,544 of our ordinary shares under our share repurchase program for a total consideration of $17.4 million.